Melbourne, Jan 11 : Australian Open champion Maria Sharapova will not be defending her title this year as she has not fully recovered from her right shoulder injury.

Next week's Australian Open has been rocked by the withdrawal of defending champion Maria Sharapova.

Sharapova's management contacted Melbourne Park officials today with news her right shoulder injury had not fully recovered, the Herald Sun reported.

Australian Open tournament director Craig Tiley confirmed Sharapova's battle for fitness had been lost.

"I'm obviously disappointed for Maria because she's extremely disappointed. We've been in constant contact with Maria and she's decided to withdraw because she's not ready in her rehabilitation process. She loves the Australian Open and she loves Melbourne - she's bitterly disappointed," Tiley said.

Sharapova, 23, has not played since Montreal in August 2008 because of chronic soreness in her shoulder.

Sharapova had been desperate to defend the Melbourne Park title. But she last week withdrew from a Hong Kong exhibition, triggering fears she would have to bypass the Open.

The decision comes as a massive blow to the Russian, who spent 10 weeks in Arizona rehabilitating.

"We were working hard on my strength and building up all the muscles around my shoulder," Sharapova said on her website.

"Unfortunately after my 10 weeks of shoulder rehab, I started hitting and serving again and I still felt the same exact pain that I have had in my shoulder since March," she added.

Sharapova joins Lindsay Davenport (pregnant) and Nadia Petrova (viral meningitis) as high-profile absentees. (ANI)